JP2009175528A - Focus-adjusting apparatus and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a focus-adjusting apparatus which adequately adjusts focus, and also to provide an imaging apparatus. <P>SOLUTION: The focus-adjusting apparatus includes; a stopping means 35 which restricts luminous flux passing through image-forming optical systems 31, 32, 33 and whose aperture diameter is adjustable; a phase difference-detecting means 21 which detects the quantity of image misalignment due to light from different areas of the pupils of the optical systems; a contrast-detecting means 21 which detects evaluation values concerning contrast of images in association with the focus adjusting positions of the optical systems; and focus-adjusting means 21, 36 which make focus adjustment to the optical systems on the basis of the quantity of the image misalignment, in a state in which the stopping means is adjusted to a first aperture diameter D1, and then make focus adjustment to the optical systems on the basis of the evaluation values in a state in which the stopping means is adjusted to a second aperture diameter D2 which is larger than the first aperture diameter. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a focus adjustment device and an imaging device.

An imaging apparatus having an autofocus function is known that performs focus control based on an evaluation value of a phase difference detection method and then performs focus control based on an evaluation value of a contrast method (Patent Document 1). .

JP 2003-156777 A

However, when the aperture stop is large, the defocus amount detection range by the phase difference detection method is narrowed, so that there is a problem that the focus cannot be adjusted appropriately.

The problem to be solved by the present invention is to provide a focus adjustment device and an imaging device capable of appropriately adjusting the focus.

  The present invention solves the above problems by the following means. In addition, although the code | symbol corresponding to drawing which shows embodiment of this invention is attached | subjected and demonstrated, this code | symbol is only for making an understanding of this invention easy, and is not the meaning which limits this invention.

[1] A focus adjusting apparatus according to a first aspect of the present invention includes an aperture means (35) capable of adjusting an aperture diameter for limiting a light beam passing through an optical system (31, 32, 33) for forming an image;
Phase difference detection means (21) for detecting an image shift amount due to light from different regions of the pupil of the optical system;
Contrast detection means (21) for detecting an evaluation value related to the contrast of the image in association with a focus adjustment position of the optical system;
In the state where the aperture means is adjusted to the first aperture diameter (D1), after the focus adjustment of the optical system is performed based on the shift amount of the image, the aperture means is set to a second larger than the first aperture diameter. Focus adjustment means (21, 36) for adjusting the focus of the optical system based on the evaluation value in a state adjusted to the aperture diameter (D2).

[2] The focus adjustment apparatus according to the second aspect of the present invention is the pupil of the optical system at a plurality of focus detection positions (22a to 22e) on the planned focal plane where an image is formed by the optical system (31, 32, 33). Phase difference detection means (21) for detecting an image shift amount due to light from different regions of
Contrast detection means (21) for detecting an evaluation value related to the contrast of the image in association with a focus adjustment position of the optical system at the plurality of focus detection positions;
Based on the shift amount of the image at the plurality of focus detection positions, at least one focus detection position is selected from the plurality of focus detection positions, and the image shift by the phase difference detection unit at the selected focus detection position. Focus adjusting means (21, 36) for adjusting the focus of the optical system based on the evaluation value by the contrast detecting means at the selected focus detection position after performing the focus adjustment of the optical system based on the amount; , Provided.

[3] A focus adjustment device according to a third aspect of the invention is a phase difference detection means (21) for detecting an image shift amount due to light from different areas of the pupil of the optical system (31, 32, 33) for forming an image. When,
Contrast detection means (21) for detecting an evaluation value related to the contrast of the image in association with a focus adjustment position of the optical system;
After performing the focus adjustment of the optical system based on the shift amount of the image, based on the evaluation value by the contrast detection unit using an image in a range smaller than the detection range of the image used for the focus adjustment, And a focus adjusting means (21, 36) for adjusting the focus of the optical system.

[4] A focus adjustment device according to a fourth aspect of the invention is a phase difference detection means (21) for detecting an image shift amount due to light from different regions of the pupil of the optical system (31, 32, 33) for forming an image. When,
Contrast detection means (21) for detecting an evaluation value related to the contrast of the image in association with a focus adjustment position of the optical system;
A focus for selecting whether or not to perform focus adjustment of the optical system based on an evaluation value by the contrast detection unit according to the characteristics of the image after performing focus adjustment of the optical system based on the image shift amount. And adjusting means (21, 36).

  In this case, the characteristic of the image is a spatial frequency characteristic of the image, and when the spatial frequency characteristic of the image is a high frequency equal to or higher than a predetermined value, focus adjustment by the contrast detection unit can be performed. .

[5] A focus adjustment apparatus according to a fifth aspect of the invention is a phase difference detection means (21) for detecting an image shift amount due to light from different regions of the pupil of the optical system (31, 32, 33) for forming an image. When,
Contrast detection means (21) for detecting an evaluation value related to the contrast of the image in association with a focus adjustment position of the optical system;
After performing the focus adjustment of the optical system based on the image shift amount by the phase difference detection means, the focus adjustment of the optical system based on the focus evaluation value by the contrast detection means according to the optical characteristics of the optical system. Focus adjustment means (21, 36,) for selecting whether to perform or not is provided.

[6] In the above invention, the phase difference detecting means (21) includes a focus detection pixel (222) having a photoelectric conversion unit (2222, 2223) that receives a pair of focus detection light beams from different regions of the pupil of the optical system. ) And first calculation means (21) for calculating a phase difference between a pair of images formed by the pair of focus detection light beams based on output data of the focus detection pixels. Including
The contrast detection means (21) forms the light beam based on the second image sensor (22) in which the imaging pixels (221) receiving the light beam passing through the optical system are arranged, and the output data of the imaging pixel. And a second calculation means (21) for calculating an evaluation value related to the contrast of the image.

In this case, the first imaging element (22) and the second imaging element (22) are one imaging element, and the focus detection pixel (222) and the imaging pixel (221) are the imaging surface of the same imaging element. It can be configured to be arranged close to the top.

The one image sensor (22) includes a plurality of the imaging pixels (221R, 221G, 221B) having different spectral sensitivity characteristics arranged according to a predetermined arrangement,
The focus detection pixel (222) can be configured to be arranged at a position corresponding to the imaging pixel (221G) having the highest spectral density characteristic in the array.

[7] An imaging apparatus according to the present invention includes the focus adjustment apparatus and an imaging element (22) that captures an image via the optical system.

  According to the present invention, it is possible to adjust the focus appropriately.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a main part configuration diagram showing a digital camera 1 according to an embodiment of the present invention. A digital camera 1 according to the present embodiment (hereinafter simply referred to as a camera 1) includes a camera body 2 and a lens barrel 3, and the camera body 2 and the lens barrel 3 are detachably coupled by a mount unit 4. Yes.

The lens barrel 3 includes a photographic optical system including lenses 31, 32 and 33 and a diaphragm 34.

The focus lens 32 is provided so as to be movable along the optical axis of the light beam L1 of the lens barrel 3, and its position is adjusted by the focus lens drive motor 37 while its position is detected by the encoder 34.

The specific configuration of the moving mechanism along the optical axis 2 of the focus lens 32 is not particularly limited. For example, a rotating cylinder is rotatably inserted into a fixed cylinder fixed to the lens barrel 3, a helicoid groove (spiral groove) is formed on the inner peripheral surface of the rotating cylinder, and the focus lens 32 is fixed. The end of the lens frame is fitted into the helicoid groove. Then, by rotating the rotating cylinder by the focus lens drive motor 37, the focus lens 32 fixed to the lens frame moves linearly along the optical axis L1. The lens barrel 3 is provided with lenses 31 and 33 other than the focus lens 32. Here, the embodiment will be described by taking the focus lens 32 as an example.

As described above, the focus lens 32 fixed to the lens frame by rotating the rotary cylinder with respect to the lens barrel 3 moves straight in the direction of the optical axis L1, but the focus lens drive motor 37 as its drive source is the lens. The lens barrel 3 is provided. The focus lens drive motor 37 and the rotary cylinder are connected by, for example, a transmission composed of a plurality of gears. When the drive shaft of the focus lens drive motor 37 is driven to rotate in any one direction, it is transmitted to the rotary cylinder at a predetermined gear ratio. Then, when the rotating cylinder rotates in any one direction, the focus lens 32 fixed to the lens frame moves linearly in any direction of the optical axis L1. When the drive shaft of the focus lens drive motor 37 is rotationally driven in the reverse direction, the plurality of gears constituting the transmission also rotate in the reverse direction, and the focus lens 32 moves straight in the reverse direction of the optical axis L1. .

The position of the focus lens 32 is detected by the encoder 34. As described above, the position of the focus lens 32 in the optical axis L1 direction correlates with the rotation angle of the rotating cylinder, and can be obtained by detecting the relative rotation angle of the rotating cylinder with respect to the lens barrel 3, for example.

As the encoder 34 of this example, the rotation of the rotating disk connected to the rotational drive of the rotating cylinder is detected by an optical sensor such as a photo interrupter, and a pulse signal corresponding to the number of rotations is output. The brush contact provided on either one of the rotary printed circuit boards provided on either one of the rotating cylinders is brought into contact with the encoder pattern on the surface, and the moving amount of the rotating cylinder (either in the rotating direction or in the optical axis direction may be used). ) That detects a change in the contact position according to the detection circuit using a detection circuit can be used.

The focus lens 34 can move in the direction of the optical axis L1 from the end on the camera body side (also referred to as the closest end) to the end on the subject side (also referred to as the infinite end) by the rotation of the rotating cylinder described above. it can. Incidentally, the current position information of the focus lens 32 detected by the encoder 34 is sent to the camera control unit 21 to be described later via the lens control unit 36, and the focus lens driving motor 37 calculates the focus calculated based on this information. The driving position of the lens 32 is driven by a command signal sent from the camera control unit 21 via the lens control unit 36.

  The diaphragm 34 is configured such that the aperture diameter around the optical axis L1 can be adjusted in order to limit the amount of light flux that passes through the photographing optical system and reaches the image sensor 22 and to adjust the blur amount. The adjustment of the aperture diameter by the diaphragm 34 is performed, for example, by sending an appropriate aperture diameter calculated in the automatic exposure mode from the camera control unit 21 via the lens control unit 36. Further, the set aperture diameter is input from the camera control unit 21 to the lens control unit 36 by a manual operation by the operation unit 27 provided in the camera body 2. The aperture diameter of the aperture 34 is detected by an aperture aperture sensor (not shown), and the lens controller 36 recognizes the current aperture diameter.

In this embodiment, in addition to the adjustment of the aperture diameter at the time of photographing, the aperture diameter is controlled at the time of focus adjustment, which will be described later.

On the other hand, the camera body 2 is provided with an imaging element 22 that receives the light beam L1 from the photographing optical system on a planned focal plane of the photographing optical system. The image sensor 22 is composed of a device such as a CCD, converts the received optical signal into an electrical signal, and sends it to the camera control unit 21. The captured image information sent to the camera control unit 21 is sequentially sent to the liquid crystal drive circuit 24 and displayed on the electronic viewfinder 25 of the observation optical system. When the shutter is pressed, the captured image information is It is recorded in the memory 23 which is a recording medium. The memory 26 can be either a removable card type memory or a built-in memory. Details of the structure of the image sensor 22 will be described later.

  The camera body 2 is provided with an observation optical system for observing an image picked up by the image pickup device 22. The observation optical system of this example includes an electronic viewfinder (EVF) 25 made up of a liquid crystal display element, a liquid crystal drive circuit 24 for driving the viewfinder, and an eyepiece lens 26. The liquid crystal drive circuit 26 reads captured image information captured by the image sensor 22 and sent to the camera control unit 21 and drives the electronic viewfinder 25 based on the read image information. As a result, the user can observe the current captured image through the eyepiece lens 26. In place of or in addition to the observation optical system using the optical axis L2, a liquid crystal display can be provided on the back surface of the camera body 2, and a captured image can be displayed on the liquid crystal display.

A camera control unit 21 is provided in the camera body 2. The camera control unit 21 is electrically connected to the lens control unit 36 through an electrical signal contact unit 41 provided on the mount unit 4, receives lens information from the lens control unit 36, and defocuses to the lens control unit 36. Send information such as volume and aperture diameter. In addition, the camera control unit 21 reads out image information from the image sensor 22 as described above, performs predetermined information processing as necessary, and outputs the information to the liquid crystal driving circuit 24 and the memory 23 of the electronic viewfinder 25. The camera control unit 21 controls the entire camera 1 such as correction of captured image information and detection of a focus adjustment state and an aperture adjustment state of the lens barrel 3.

The operation unit 27 is a shutter release button or an input switch for the user to set various operation modes of the camera 1. Switching between the auto focus mode / manual focus mode and the one-shot mode / continuous mode are also possible. The as mode can be switched. Here, the one-shot mode is a mode in which the focus position once adjusted is fixed, and shooting is performed at the focus position. On the other hand, the continuous mode is a focus in accordance with the subject without fixing the focus position. This is a mode for adjusting the position. Various modes set by the operation unit 27 are sent to the camera control unit 21, and the operation of the entire camera 1 is controlled by the camera control unit 21.

Next, the image sensor 22 according to the present embodiment will be described.

2 is a front view showing the focus detection position on the imaging surface of the image sensor 22, FIG. 3A is a front view schematically showing the arrangement of the focus detection pixels 222 by enlarging the IIIA part of FIG. 2, and FIG. FIG. 3 is a front view schematically showing an array of focus detection pixels 222 by enlarging a IIIB portion in FIG. 2.

As shown in FIGS. 3A and 3B, the imaging element 22 of the present embodiment includes a color filter in which a plurality of imaging pixels 221 are two-dimensionally arranged on the plane of the imaging surface and transmit a green wavelength region. A green pixel G, a red pixel R having a color filter that transmits a red wavelength region, and a blue pixel B having a color filter that transmits a blue wavelength region are arranged in a so-called Bayer Arrangement. That is, in four adjacent pixel groups 223 (dense square lattice arrangement), two green pixels are arranged on one diagonal line, and one red pixel and one blue pixel are arranged on the other diagonal line. The image sensor 22 is configured by repeatedly arranging the pixel group 223 on the imaging surface of the image sensor 22 in a two-dimensional manner with the Bayer array pixel group 223 as a unit.

The unit pixel group 223 may be arranged in a dense hexagonal lattice arrangement other than the dense square lattice shown in the figure. Further, the configuration and arrangement of the color filters are not limited to this, and an arrangement of complementary color filters (green: G, yellow: Ye, magenta: Mg, cyan: Cy) can also be adopted.

4A is an enlarged front view showing one of the imaging pixels 221 and FIG. 7A is a cross-sectional view. One imaging pixel 221 includes a microlens 2211, a photoelectric conversion unit 2212, and a color filter (not shown). As shown in the cross-sectional view of FIG. 7A, the photoelectric conversion unit is formed on the surface of the semiconductor circuit substrate 2213 of the imaging element 22. 2212 is built in and a microlens 2211 is formed on the surface. The photoelectric conversion unit 2212 is configured to receive an imaging light beam passing through an exit pupil (for example, F1.0) of the imaging optical system 31 by the micro lens 2211 and receives the imaging light beam IB.

The color filter of this embodiment is provided between the microlens 2211 and the photoelectric conversion unit 2212. The spectral sensitivities of the color filters of the green pixel G, the red pixel R, and the blue pixel B are shown in FIG. It is said to be as follows.

Returning to FIGS. 2, 3 </ b> A, and 3 </ b> B, focus detection pixels 222 are arranged in place of the above-described imaging pixels 221 at the center of the imaging surface of the imaging element 22 and at five locations that are vertically and horizontally symmetrical from the center. Focus detection pixel rows 22a, 22b, 22c, 22d, and 22e are provided. As shown in FIGS. 3A and 3B, one focus detection pixel column is configured by arranging a plurality of focus detection pixels 222 in a horizontal row (22a, 22d, 22e) or a vertical row (22b, 22c). . The focus detection pixels 222 of this example are densely arranged without providing a gap at the positions of the green pixels G and blue pixels B of the image pickup pixels 221 arranged in the Bayer array.

Note that the positions of the focus detection pixel rows 22a to 22e shown in FIG. 2 are not limited to the illustrated positions, and may be any one, two, or three locations, and may be at six or more locations. It can also be arranged. In actual focus detection, the user can select a desired focus detection pixel row by manually operating the operation unit 27 from among a plurality of focus detection pixel rows 22a to 22e.

4B is an enlarged front view showing one of the focus detection pixels 222, and FIG. 7B is a cross-sectional view thereof. As shown in FIG. 4B, the focus detection pixel 222 includes a micro lens 2221 and a pair of photoelectric conversion units 2222 and 2223. As shown in the cross-sectional view of FIG. 7B, the surface of the semiconductor circuit substrate 2213 of the imaging element 22 is formed. The photoelectric conversion parts 2222 and 2223 are built in, and the micro lens 2221 is formed on the surface thereof. The pair of photoelectric conversion units 2222 and 2223 have the same size and are arranged symmetrically (22a, 22d, 22e) or vertically symmetrical (22b, 22c) with respect to the optical axis of the microlens 2221. The photoelectric conversion units 2222 and 2223 are configured to receive a pair of light beams that pass through a specific exit pupil (for example, F2.8) of the photographing optical system 31 by the micro lens 2221. That is, as shown in FIG. 7B, one photoelectric conversion unit 2222 of the focus detection pixel 222 receives one light beam AB1, while the other photoelectric conversion unit 2223 of the focus detection pixel 222 is an optical axis of the micro lens 2221. In contrast, a light beam AB2 that is symmetrical with the light beam AB1 is received.

Note that the focus detection pixel 222 is not provided with a color filter, and its spectral characteristics are a combination of the spectral characteristics of a photodiode that performs photoelectric conversion and the spectral characteristics of an infrared cut filter (not shown). . FIG. 6 shows the spectral characteristics of the focus detection pixel 222. The relative sensitivity is a spectral characteristic obtained by adding the sensitivity of the blue pixel B, the green pixel G, and the red pixel R of the imaging pixel 221 shown in FIG. The light wavelength region where the sensitivity appears is a region including the light wavelength regions of the sensitivity of the blue pixel B, the green pixel G, and the red pixel R of the imaging pixel 221 shown in FIG. However, it may be configured to include one of the same color filters as the imaging pixel 221, for example, a green filter.

In addition, although the photoelectric conversion units 2222 and 2223 of the focus detection pixel 222 illustrated in FIG. 4B have a semicircular shape, the shape of the photoelectric conversion units 2222 and 2223 is not limited to this, and other shapes such as an elliptical shape, a rectangular shape, and the like. It can also be a shape or a polygonal shape.

Here, a so-called pupil division phase difference detection method for adjusting the focus based on the output of the focus detection pixel 222 described above will be described.

FIG. 8 is a cross-sectional view taken along the line VIII-VIII in FIGS. 3A and 3B. The focus detection pixel 222-1 disposed on the photographing optical axis L and the focus detection pixel 222-2 adjacent thereto are shown in FIG. It shows that the light beams AB1-1, AB2-1, AB2-1, AB2-2 irradiated from the distance measuring pupils 341, 342 of the exit pupil 34 are received. However, for other focus detection pixels, the pair of photoelectric conversion units receive a pair of light beams emitted from the pair of distance measurement pupils 341 and 342.

Here, the exit pupil 34 is an image set at a position D in front of the microlens 2221 of the focus detection pixel 222 disposed on the planned focal plane of the lens barrel 3. The distance D is a value uniquely determined according to the curvature and refractive index of the microlens, the distance between the microlens and the photoelectric conversion unit, and the distance D is referred to as a distance measurement pupil distance. The distance measurement pupils 341 and 342 are images of the photoelectric conversion units 2222 and 2223 projected by the micro lens 2221 of the focus detection pixel 222.

In the figure, the arrangement direction of the focus detection pixels 222-1 and 222-2 is coincident with the arrangement direction of the pair of distance measurement pupils 341 and 342.

The microlenses 2221-1 and 221-2 of the focus detection pixel 222 are disposed in the vicinity of the planned focal plane of the lens barrel 3, and are disposed behind the microlens 2221-1 disposed on the optical axis L. The shapes of the paired photoelectric conversion units 2222-1 and 22223-1 are projected onto the exit pupil 34 separated by the distance measuring pupil distance D, and the projected shapes form the distance measuring pupils 341 and 342.

Similarly, the shape of the pair of photoelectric conversion units 2222-2 and 2223-2 arranged behind the microlens 2221-2 arranged away from the optical axis L is separated by the distance measuring pupil distance D. Projected onto the exit pupil 34, the projection shape forms distance measuring pupils 341 and 342.

That is, on the exit pupil 34 at the distance measurement pupil distance D, the projection direction of each pixel 222 is set so that the projection shapes (distance detection pupils 341 and 342) of the photoelectric conversion units 2222 and 2223 of the focus detection pixels 222 match. It has been decided.

Note that the photoelectric conversion unit 2222-1 of the focus detection pixel 222-1 is placed on the microlens 2222-1 by one focus detection light beam AB1-1 that passes through one distance measuring pupil 341 and travels toward the microlens 2222-1. A signal corresponding to the intensity of the formed image is output. In contrast, the photoelectric conversion unit 2223-1 has an image formed on the microlens 2221-1 by the other focus detection light beam AB2-1 that passes through the other distance measuring pupil 342 and travels toward the microlens 2222-1. A signal corresponding to the intensity of the signal is output.

Similarly, the photoelectric conversion unit 2222-2 of the focus detection pixel 222-2 passes through one distance measuring pupil 341 and is focused on the microlens 2221-2 by one focus detection light beam AB1-2 that goes to the microlens 2221-2. A signal corresponding to the intensity of the image formed is output. On the other hand, the photoelectric conversion unit 2223-2 is an image formed on the microlens 221-2 by the other focus detection light beam AB <b> 2-2 that passes through the other distance measuring pupil 342 and travels toward the microlens 221-2. A signal corresponding to the intensity of the signal is output.

A plurality of the focus detection pixels 222 are arranged in a straight line as shown in FIGS. 3A and 3B, and the outputs of the pair of photoelectric conversion units 2222 and 2223 of each focus detection pixel 222 are the distance measurement pupil 341 and the distance measurement pupil. Data relating to the intensity distribution of a pair of images formed on the focus detection pixel array by the focus detection light beams AB1 and AB2 passing through the distance measurement pupil 341 and the distance measurement pupil 342 by grouping them into output groups corresponding to each of 342. Is obtained. By applying an image shift detection calculation process such as a correlation calculation process or a phase difference detection process to the intensity distribution data, an image shift amount by a so-called pupil division phase difference detection method can be detected.

Then, a conversion calculation is performed on the obtained image shift amount according to the center-of-gravity interval of the pair of distance measuring pupils, thereby obtaining a current focal plane with respect to the planned focal plane (the focal point corresponding to the position of the microlens array on the planned focal plane). The deviation of the focal plane at the detection position, that is, the defocus amount can be obtained.

The camera control unit 21 executes the image shift amount calculation and the defocus amount calculation based on the pupil division phase difference detection method.

Incidentally, focus detection pixels 222a and 222b shown in FIGS. 9A, 9B, and 10 may be used in place of the focus detection pixel 222 of the present embodiment. 9A and 9B are front views schematically showing the arrangement of pixels according to another embodiment of the present invention, enlarged front views corresponding to the IIIA part and the IIIB part of FIG. 2, respectively, and FIG. It is a front view which expands and shows a pair of focus detection pixels 222a and 222b of 9A and 9B.

In the embodiment shown in FIGS. 3A, 3B, and 4B, the focus detection pixel 222 having a pair of photoelectric conversion units 2222 and 2223 is used, whereas FIGS. 9A, 9B, and 10 show the focus detection pixel 222. In the illustrated embodiment, a pixel having photoelectric conversion units 2224 and 2225 paired with each of the pair of focus detection pixels 222a and 222b is used.

A focus detection pixel 222a illustrated in FIG. 10 includes a microlens 2221 and a photoelectric conversion unit 2224, and the photoelectric conversion unit 2224 is formed on the surface of the semiconductor circuit substrate 2213 of the image sensor 22 as in the cross-sectional view illustrated in FIG. 7B. The microlens 2221 is formed on the surface. The photoelectric conversion unit 2224 is disposed on the left side of a position symmetrical with respect to the optical axis of the micro lens 2221.

On the other hand, the focus detection pixel 222b shown in FIG. 10 also includes a microlens 2221 and a photoelectric conversion unit 2225. Like the cross-sectional view shown in FIG. A conversion unit 2225 is built, and a microlens 2221 is formed on the surface thereof. The photoelectric conversion unit 2225 is disposed on the right side of a position symmetrical to the optical axis of the micro lens 2221.

As shown in FIGS. 9A and 9B, the pair of focus detection pixels 222a and 222b are arranged in a left-right line (22a, 22d, 22e) or a vertical line (22b, 22c) from the center of the image sensor 22, and are used for photographing optics. A pair of light beams passing through the exit pupil of the system 31 is received by the photoelectric conversion units 2224 and 2225 of the pair of focus detection pixels 222a and 222b, respectively.

As described above, even when a pair of focus detection pixels 222a and 222b configured by different pixels is used, the image shift amount by the pupil division phase difference detection method is detected based on the output results of the pair of photoelectric conversion units 2224 and 2225. can do.

In addition to this, there is an advantage that the configuration of the output readout circuit from the pixels constituting the image sensor 22 is simplified.

Returning to FIG. 1, when the image sensor 22 performs an autofocus search with the autofocus switch provided in the operation unit 27 turned on, the contrast in a predetermined area (22a to 22e) of the image that has passed through the focus lens 32 is returned. The value is output to the camera control unit 21.

The camera control unit 21 calculates a focus evaluation value from the image output sent from the image sensor 22. This focus evaluation value can be obtained, for example, by extracting a high-frequency component of the image output from the image sensor 22 using a high-frequency transmission filter and integrating it to detect the focus voltage. It can also be obtained by extracting high-frequency components using two high-frequency transmission filters having different cutoff frequencies and integrating them to detect the focus voltage.

Further, the camera control unit 21 sends a control signal to the lens control unit 36 to drive the focus lens 32 at a predetermined sampling interval (distance), obtains a focus evaluation value at each position, and the focus evaluation value is maximum. The position of the focus lens 32 is determined by using an arithmetic method such as an interpolation method.

A method of obtaining the maximum focus evaluation value by this interpolation method will be described with reference to FIG. FIG. 11 is a graph for explaining the focus determination of the camera 1 according to the present embodiment. Here, a three-point interpolation method will be described.

The circles shown in FIG. 11 indicate sampling points for focus evaluation values. For example, it is assumed that focus evaluation values at eight locations P1 to P8 are acquired in the search range of the focus lens 32. A curve indicated by a broken line indicates a profile of the focus evaluation value, and has a peak at the lens position Px.

  Of the eight focus evaluation values acquired, the focus evaluation value P5 is the maximum, but in the three-point interpolation method, the maximum focus evaluation value P5 and the focus evaluation values P4 and P6 positioned before and after the focus evaluation value P5 are obtained. The focal position Px of the lens is calculated using this. First, a straight line L1 passing through the minimum point P6 among the maximum point P5 and the three points is calculated. When the slope of the straight line L1 is K, the straight line L2 passing through the remaining point P4 with the slope of −K is calculated. And the lens position coordinate of the intersection of the straight line L1 and the straight line L2 is calculated | required. The lens position coordinate of this intersection is taken as the focus position Px of the focus lens 32.

The focus position Px of the focus lens 32 thus obtained is sent from the camera control unit 21 to the lens control unit 36, and the focus lens drive motor 37 is controlled to move the focus lens 32 to the focus position.

When the autofocus switch of the operation unit 27 is turned off, the user can perform a manual focusing operation by rotating the focus ring of the lens barrel 3.

Next, an operation example of the camera 1 according to this embodiment will be described. 12A and 12B are flowcharts showing the operation of the camera 1 according to this embodiment.

First, after confirming that the power source of the camera 1 is turned on in step S1, the process proceeds to step S2, and it is confirmed whether or not the setting of the operation unit 27 is the autofocus mode.

  When the setting of the operation unit 27 is the autofocus mode, the process proceeds to step S3, where a command signal is sent from the camera control unit 21 to the lens control unit 36, and the aperture diameter of the diaphragm 35 is set to D1. The opening diameter D1 is an opening diameter that is relatively smaller than an opening diameter D2 in step S22 described later.

  In general, the response performance of the focus adjustment by the pupil division type phase difference detection method is faster than the response performance of the focus adjustment by the contrast detection method, while the focus detection accuracy by the contrast detection method is the pupil division type phase difference detection method. It can be said that the accuracy is higher than the detection accuracy of

  However, if the subject image contains a lot of low-frequency components, the contrast evaluation value changes very little even near the in-focus point, and the contrast detection method is not always more accurate, and the pupil-divided phase difference Even if the focus adjustment is uniformly performed by the contrast detection method after performing the focus adjustment according to the result of the detection method, the response performance is deteriorated and the accuracy of the focus adjustment is not improved.

  Further, when focus adjustment is performed by simultaneously performing focus detection at a plurality of focus detection positions 22a to 22e on the image sensor 22, focus detection and contrast detection by the pupil division type phase difference detection method are performed at all focus detection positions. When focus detection is performed by the method, there is a problem that the response performance of focus adjustment deteriorates.

  Furthermore, when performing focus adjustment according to the result of the pupil division type phase difference detection method and then performing focus detection by the contrast detection method, the range of images used for the pupil division type phase difference detection method and the image range used for the contrast detection method are described. If the range is the same, focus detection accuracy may not be improved. For example, when performing rough focus adjustment, there is no problem if subject images with slightly different distances coexist in the image range used in the pupil division type phase difference detection method, but the contrast detection method is used for the same image range. If focus detection is performed with, accurate focus may not be detected. In addition, when performing rough focus adjustment, there is no major problem even if a low-frequency component and a high-frequency component coexist in the image range used in the pupil division type phase difference detection method. When focus detection is performed using the contrast detection method, an accurate in-focus point may not be detected.

  In addition, when focus detection is performed by contrast detection after performing focus adjustment according to the result of the pupil division type phase difference detection method, the pupil division type phase difference detection method has large defocus detection performance, that is, can be detected. The maximum image shift amount is required to be as large as possible, while the contrast detection method is required to have high focus detection performance, but the pupil division type phase difference detection method and the contrast detection method are performed with the same aperture diameter. In some cases, the two required performances cannot be satisfied simultaneously.

  In view of the above problems, the camera 1 of the present embodiment is roughly based on the result of focus detection by the pupil division type phase difference detection method in the initial stage of focus adjustment, that is, when there is a case where there is a large defocus. Focus adjustment is performed quickly, and in the final stage of focus adjustment, that is, in the vicinity of the in-focus point, highly accurate focus adjustment is performed based on the result of focus detection by the contrast detection method.

  FIG. 13 is a graph showing the relationship between the defocus amount and the image shift amount (the phase difference amount detected by the pupil division type phase difference detection method). The aperture diameter of the diaphragm 35 is relatively small D1 and large D2. This is a comparison of the cases. Although the maximum image shift amount that can be detected is limited by the length in the arrangement direction of the focus detection pixel rows 22a to 22e provided in the image sensor 22, when the maximum image shift amount that can be detected is the same, the aperture 35 is opened. The defocus amount that can be detected increases when the diameters D1 and D2 are relatively small (D1). As shown in the figure, when the maximum image shift amount is Zmax, the defocus amount DF1 detectable by the aperture diameter D1 is compared with the defocus amount DF2 detectable by the aperture diameter D2, and DF1> DF2. .

  For this reason, in step S3, the aperture 35 is opened relatively small so that the defocus amount can be detected using the pupil division type phase difference detection method at the initial stage of focus detection, which may be largely defocused. Set to aperture D1.

  In step S <b> 4, an exposure operation is performed by the image sensor 22, and data of the imaging pixel 221 is read to the camera control unit 21 and displayed on the electronic viewfinder 25 via the liquid crystal driving circuit 24. Thereby, the user can visually recognize the moving image of the subject.

  In step S <b> 5, a pair of image data corresponding to the pair of images is read out to the camera control unit 21 from the focus detection pixel array 222 arranged at the five focus detection positions 22 a to 22 e of the image sensor 22. In this case, when a specific focus detection pixel row is selected by a user's manual operation, only data from the focus detection pixel of the focus detection pixel row is read out. Then, an image shift detection calculation process (correlation calculation process) is executed based on the read pair of image data, the image shift amounts at the five focus detection positions 22a to 22e are calculated, and the image shift amount is further defocused. Convert to quantity.

Here, an example of image shift detection calculation processing (correlation calculation processing) based on the read pair of image data will be briefly described.

In the pair of images detected by the focus detection pixel 222, the distance measurement pupils 341 and 342 may be shielded by the diaphragm 35 of the lens barrel 3, and the light quantity balance may be lost. Therefore, in the present embodiment, a correlation calculation of a type capable of maintaining the image shift detection accuracy is performed with respect to the loss of light amount balance.

First, a pair of image data sequences read out from the focus detection pixel sequence are A1 ₁ to A1 _M and A2 _{1 to} A2 _M (M is the number of data), the following correlation calculation formula (Formula 1) is performed, and the correlation amount C (K) is calculated.

<< Equation 1 >>
C (k) = Σ | A1 _n · A2 _{n + 1 + k} −A2 _{n + k} · A1 _{n + 1} |
In Equation 1, the Σ operation indicates a cumulative operation (sum operation) with respect to n, and the range of n is a range in which data of A1 _n , A1 _{n + 1} , A2 _{n + k} , A2 _{n + 1 + k} exists according to the image shift amount k. Limited. Further, the image shift amount k is an integer, and is a relative shift amount with the data interval of the data string as a unit.

  As shown in FIG. 14A, the calculation result of Equation 1 shows that the correlation amount C (k) is minimal (small) in a shift amount with high correlation between a pair of data (k = kj = 2 in FIG. 14A). The higher the degree of correlation).

Next, the shift amount x that gives the minimum value C (x) with respect to the continuous correlation amount is obtained by using the three-point interpolation method according to Equations 2 to 5.

<< Equation 2 >>
x = kj + D / SLOP

<< Equation 3 >>
C (x) = C (kj)-| D |

<< Equation 4 >>
D = {C (kj-1) -C (kj + 1)} / 2

<< Equation 5 >>
SLOP = MAX {C (kj + 1) -C (kj), C (kj-1) -C (kj)}
Then, whether or not the shift amount x calculated by Expression 2 is reliable is determined as follows.

As shown in FIG. 14B, when the degree of correlation between a pair of data is low, the value of the minimal value C (x) of the interpolated correlation amount is large. Therefore, when C (x) is equal to or greater than a predetermined threshold value, it is determined that the reliability of the calculated shift amount is low, and the calculated shift amount x is canceled.

Alternatively, in order to normalize C (x) with the contrast of data, when the value obtained by dividing C (x) by SLOP that is proportional to the contrast is equal to or greater than a predetermined value, the reliability of the calculated shift amount Is determined to be low, and the calculated shift amount x is canceled.

Alternatively, when SLOP that is proportional to the contrast is equal to or less than a predetermined value, it is determined that the subject has low contrast and the reliability of the calculated shift amount is low, and the calculated shift amount x is canceled.

Further, as shown in FIG. 14C, when the correlation between the pair of data is low and the correlation amount C (k) does not drop between the shift ranges kmin to kmax, the minimum value C (x) is obtained. In such a case, it is determined that the focus cannot be detected.

The correlation calculation formula is not limited to Formula 1 described above, and other known correlation formulas can also be used.

  When it is determined that the calculated shift amount x is reliable, the image shift amount shft is obtained by the following formula 6.

<< Equation 6 >>
shft = PY · x
In Expression 6, PY is a detection pitch (pitch of focus detection pixels).

Finally, the defocus amount def is obtained by multiplying the image shift amount shft calculated by Equation 6 by a predetermined conversion coefficient k corresponding to the aperture diameter D1 of the diaphragm 35 when detection is performed by the pupil division type phase difference detection method. Ask for.

<< Equation 7 >>
def = k · shft
Returning to FIG. 12A, when the defocus amounts of the five focus detection positions 22a to 22e are obtained, a predetermined selection criterion is selected from the obtained defocus amounts of the five focus detection positions 22a to 22e in step S6. One focus detection position is selected based on the above. This predetermined selection criterion is a criterion such as a focus detection position where a defocus amount indicating the shortest distance among five defocus amounts is calculated. However, this selection criterion can be appropriately changed according to the design concept of the camera 1.

  In step S7, it is determined whether or not the absolute value of the defocus amount at the selected focus detection position is within a predetermined value. This predetermined value is an in-focus range that can be regarded as in-focus without driving the focus lens 32.

  If the absolute value of the defocus amount is not within the predetermined value in step S7, the process proceeds to step S8, a drive signal is sent from the camera control unit 21 to the focus lens drive motor 37 via the lens control unit 36, and the focus lens 32. After moving to the in-focus position, the process returns to step S1, and steps S1 to S7 are repeated.

Although illustration is omitted, if it is determined in step S7 that focus detection is impossible, the process proceeds to step S8, where a scan drive command is transmitted to the lens control unit 36, and the focus lens 32 is moved from the infinite end. After searching for the in-focus position by driving the scanning between the near ends, the process returns to step S1 and the above operation is repeated.

  When the absolute value of the defocus amount is within the predetermined value in step S7, that is, when the focus adjustment by the pupil division type phase difference detection method is completed, the process proceeds to step S9, where the setting of the autofocus mode of the operation unit 27 is continuous. Determine whether the mode or one-shot mode. As described above, the continuous mode is a mode in which after the in-focus state is achieved, the in-focus position search is continued according to the subject and the focus lens 32 is moved to the in-focus position. The one-shot mode is a mode in which the focus lens 32 is fixed and the focus is locked once focusing is achieved.

  If the continuous mode is selected in step S9, the process proceeds to step S10 to determine whether or not the shutter has been released. If the release button of the operation unit 27 is not pressed, the process returns to step S1 and the processes in steps S1 to S9 are performed. repeat.

If it is detected in step S10 that the release button has been pressed, the process proceeds to step S11, where an aperture adjustment command is transmitted to the lens control unit 36, and the aperture value of the aperture 35 is set to the user or an automatically set control F value. To. After the aperture control is completed, image data is read from the imaging pixel 221 and all focus detection pixels 222 of the imaging element 22.

Here, since the read image data of the focus detection pixels 222 is black and white data, in step S12, the pixel data in which the focus detection pixels 222 of the focus detection pixel rows 22a to 22e are located are detected as the focus data. Pixel interpolation is performed based on the image data of the imaging pixels 221 around the pixel 222. Thereby, color image data at the positions of the focus detection pixel rows 22a to 22e can be obtained.

Finally, in step S13, the image data of the imaging pixel 221 and the interpolated image data are stored in the memory 23. At this time, when a liquid crystal display is provided on the back surface of the camera body 2, the obtained image data can be thinned and displayed on the liquid crystal display.

  Returning to step S9, if it is not the continuous mode, that is, if it is the one-shot mode, the process proceeds to step S21 in FIG. 12B. In step S21, it is determined whether or not the amount of the high-frequency component of the image at the focus detection position selected in step S6 is greater than or equal to a predetermined value. If it is not greater than the predetermined value, strict focus adjustment is performed using a contrast detection method. Since the detection accuracy cannot be expected, the process jumps from step S22 to S24 and proceeds to step S25 to determine whether or not the shutter release has been performed. When the release button of the operation unit 27 is pressed, the process proceeds to step S11 in FIG. The process of steps S11 to S13 described above is executed.

  In FIG. 15, the horizontal axis represents the defocus amount, and the vertical axis represents the contrast evaluation value by the contrast detection method, and the relationship between the defocus amount and the contrast evaluation value for the image of only the high frequency component (D1 where the aperture diameter of the diaphragm 35 is small) ( The relationship between the defocus amount and the contrast evaluation value (solid line) for an image with only a high-frequency component (D2 where the aperture diameter of the diaphragm 35 is large) and an image with only a low-frequency component (D1 where the aperture diameter of the diaphragm 35 is small) It is a graph which shows the relationship (dotted line) of the defocus amount and contrast evaluation value with respect to (when D2 is large).

  As is apparent from this graph, in the case of an image containing only a low frequency component that does not include a high frequency component, there is little change in the contrast evaluation value even when the in-focus position, that is, the defocus amount is near zero. Even if focus adjustment is performed using the contrast detection method, improvement in focus detection accuracy cannot be expected, and response performance of the focus adjustment operation also deteriorates. In this example, for these reasons, the focus adjustment steps S22 to S24 by the contrast detection method are not executed.

On the other hand, if the amount of the high-frequency component of the image at the selected focus detection position is greater than or equal to a predetermined value in step S21, the process proceeds to a strict focus adjustment process using the contrast detection method in steps S22 to S24.

Here, the determination of the high frequency component in step S21 will be described with reference to FIG.

  In the upper diagram of FIG. 16, the horizontal axis is the pixel position of the image sensor 22, and the vertical axis is the image data (output value), and the adjacent imaging pixel 221 (parallel to the focus detection pixel row 222 at the selected focus detection position). The pixel data of the green pixel G) array is shown as an image waveform. The lower diagram of FIG. 16 shows a waveform obtained by subjecting the image waveform of the upper diagram to the secondary differential filter processing (digital filter processing).

  If the pixel data of the imaging pixel array (green pixel G) is G (i) (i indicates the order and position of the pixel data), the data H (i) processed by the secondary differential filter is as follows, for example: It is expressed in

<< Equation 8 >>
H (i) = | −G (i−2) + 2G (i) −G (i + 2) |
i = 1 to N
Since the low-frequency component is cut and the high-frequency component is extracted by the secondary differential filter processing, the evaluation value ΣH (i) corresponding to the amount of the high-frequency component is calculated by integrating the absolute value over the range of the pixel data. Is done.

<< Equation 9 >>
ΣH (i)> Th1
When the evaluation value ΣH (i) is equal to or greater than the predetermined value Th1, it is determined that focus adjustment accuracy can be expected by a contrast detection method using a high frequency component.

Returning to FIG. 12B, when it is determined that the amount of the high-frequency component of the image at the focus detection position selected in step S21 is greater than or equal to a predetermined value, a command signal is sent from the camera control unit 21 to the lens control unit 36 in step S22. Then, the aperture diameter of the diaphragm 35 is set to D2. This opening diameter D2 is a relatively large opening diameter compared with the opening diameter D1 of step S3 described above.

  As shown in FIG. 15, when the aperture diameter D2 of the diaphragm 35 is relatively larger than the aperture diameter D1, the change in the contrast evaluation value is larger in the vicinity of the in-focus position where the defocus amount is zero. Therefore, improvement in focus detection accuracy by the contrast detection method can be expected. In this example, for this reason, in addition to performing focus adjustment by the contrast detection method at the final stage of focus adjustment, the aperture diameter D2 of the diaphragm 35 is set to be relatively large.

  In step S23, a range of image data (pixel data) used for the contrast detection method is set.

  In the upper diagram of FIG. 16, a range R1 is a range of image data used for focus detection by the pupil division type phase difference detection method, and is set to a relatively wide range. This is because if the range of the image on which focus detection is performed in the initial stage of focus adjustment is too narrow, there is a high possibility that an image portion capable of focus detection (image portion having a relatively high contrast) will not enter that range.

  On the other hand, in order to perform high-precision focus detection by the contrast detection method at the final stage of focus adjustment, it is desirable to perform focus detection only in a portion where the high-frequency component of the image is large. This is because if the focus detection range is wide, subject images having different distances may coexist in the focus detection range, so that good contrast detection cannot be performed and focus detection accuracy may not be improved.

  For this reason, in this example, in the data subjected to the secondary differential filter processing of the pixel data as shown in the lower diagram of FIG. 16, the pixel position of the peak of the secondary differential data (the highest frequency component is the most) is centered. An image range R2 narrower than the image range R1 used for focus detection in the pupil division type phase difference detection method is set. Since this image range R2 contains a lot of high-frequency components, an improvement in focus detection accuracy of the contrast detection method can be expected.

  Returning to FIG. 12B, in step 24, the imaging operation is performed with the aperture 35 having the aperture diameter D <b> 2, the data of the imaging pixel 221 adjacent in parallel to the focus detection pixel row 222 is read, and the pixels of the imaging pixel 221 in the range R <b> 2. Contrast detection is performed on the data. Then, the focus lens 32 is moved to the in-focus position by focus adjustment control using a known hill-climbing method. In the drive control of the focus lens 32 by this hill-climbing method, the contrast evaluation value C is calculated while the focus lens 32 is driven in minute steps in a fixed direction, and the focus lens position at which the contrast evaluation value C is maximum is determined as the focus position. Finally, the focus lens 32 is moved and stopped at the in-focus position.

  As the contrast evaluation value C by the contrast detection method, the sum of adjacent differences of pixel data in the pixel data range R2 (C = Σ | G (i) −G (i + 1) |), the maximum value of adjacent differences of pixel data. (C = MAX (| G (i) −G (i + 1) |)), sum of second-order differences of pixel data (C = Σ | −G (i−1) + 2G (i) −G (i + 1) |) , Maximum value of second-order difference of pixel data (C = MAX (| −G (i−1) + 2G (i) −G (i + 1) |)), difference between maximum value and minimum value of pixel data (C = MAX (G (i))-MIN (G (i)) or the like can be used.

  Step S25 and subsequent steps are as described above.

  As described above, according to the camera of the present embodiment, the aperture diameter of the diaphragm 35 is set to a relatively small diameter D1 when performing focus adjustment of the pupil division type phase difference detection method at the initial stage of focus adjustment. At the same time, focus detection is performed at a plurality of focus detection positions using image data in a relatively wide range, so that a large defocus amount can be detected, image capture performance is improved, and rough focus is achieved with high response performance. Adjustments can be made.

  On the other hand, when performing contrast detection focus adjustment at the final stage of focus adjustment, the aperture diameter of the diaphragm 35 is set to a relatively large diameter D2, and one image data in a relatively narrow range is used. Since focus detection is performed at the focus detection position, it is possible to perform focus adjustment with high accuracy and little deterioration in response performance. In addition, when high-precision focus detection by the contrast detection method cannot be expected, or when high focus adjustment response performance is required, focus adjustment by the contrast detection method is omitted, so that high-speed focus adjustment can be performed. .

  In addition, since the focus detection pixel 222 used in the pupil division type phase difference detection method and the image pickup pixel 221 used in the contrast detection method are arranged on the same image pickup surface of the image pickup device 22, both types are used as separate image pickup devices. Compared to the case where the light beam is divided, the focus detection error caused by the relative position error between the image sensors, the light quantity when the light beam is divided into separate image sensors with a half mirror, and the insertion / retraction of the mirror Problems such as a decrease in response performance when light beams are guided to a separate image sensor in a time division manner are suppressed.

  In addition, since the imaging pixels that are adjacent in parallel to the focus detection pixel row used in the pupil division type phase difference detection method are used for focus detection by the contrast detection method, the identity of images detected by both methods is guaranteed, and both methods are used. As compared with the case where the image is performed by a separate image sensor, it is possible to suppress a focus detection error due to focus detection for different images.

  Note that the above-described embodiment can be appropriately modified as necessary.

  In the above embodiment, in the focus detection by the contrast detection method, the data of the green pixel G adjacent in parallel to the focus detection pixel column is used (Step S24 in FIG. 12B), but adjacent to the focus detection pixel column in parallel. It is also possible to detect contrast for each color using the data of the red pixel R and the blue pixel B. In addition, contrast detection can be performed using an imaging pixel having the highest output level in the vicinity of the focus detection pixel row. Furthermore, one of the pair of focus detection pixel data can be used for contrast detection, or data obtained by adding the focus detection pixel data adjacently can be used for contrast detection.

  In the above embodiment, in order to set the range of the image data used for the contrast detection method, the second order differentiation of the image data (step S23 in FIG. 12B, the lower diagram in FIG. 16) is used. The image data range is uniformly set in a predetermined range, is set using a first derivative of the image data, or is set using information on spatial frequency characteristics obtained by Fourier transforming the image data. You can also.

  In the above-described embodiment, the second-order differential filter is used as a method for detecting the high-frequency component of the image by the contrast detection method (step S21 in FIG. 12B), but the image contrast (for example, the pixel as the contrast evaluation value C described above) Sum of adjacent difference of pixel data in data range R2 (C = Σ | G (i) −G (i + 1) |), maximum value of adjacent difference of pixel data (C = MAX (| G (i) −G (i + 1)) ) |)), Sum of second-order differences of pixel data (C = Σ | −G (i−1) + 2G (i) −G (i + 1) |), maximum value of second-order differences of pixel data (C = MAX (| −G (i−1) + 2G (i) −G (i + 1) |)), difference between maximum value and minimum value of pixel data (C = MAX (G (i)) − MIN (G (i)) Etc.) and spatial frequency characteristic information obtained by Fourier transform of image data It is also possible.

  In the above embodiment, when the high-frequency component of the image is small and high-precision focus detection by the contrast detection method cannot be expected, the focus adjustment by the contrast detection method is omitted, but the contrast detection method according to the optical characteristics of the imaging optical system When it is determined that high-precision focus detection by is unnecessary, focus adjustment by the contrast detection method can be omitted. For example, if the optical system has large aberrations and high-precision focus detection is meaningless, if the aperture F value is large and high-precision focus detection is unnecessary, the aperture control F value at the time of shooting is large and high. This is the case when accurate focus detection is not necessary, or in the case of a pan focus lens with a wide focus.

  Further, in the above embodiment, when the high-frequency component of the image is small and high-precision focus detection by the contrast detection method cannot be expected, focus adjustment by the contrast detection method is omitted, but the contrast according to the focus detection positions 22a to 22e. Focus adjustment by the detection method can be omitted. For example, when the focus detection position at the center of the image sensor 22 is set for high-precision focus detection, when the focus detection position around the image sensor 22 is selected, or from the aberration at the center of the image sensor 22 This is the case when the aberration around the image sensor 22 is large and the focus detection position around the image sensor 22 is selected.

  Furthermore, in the above embodiment, when the high-frequency component of the image is small and high-precision focus detection by the contrast detection method cannot be expected, focus adjustment by the contrast detection method is omitted, but focus detection by the pupil division type phase difference detection method is omitted. When the accuracy is high, the focus adjustment by the contrast detection method can be omitted. For example, when the image shift amount is calculated, the parameter C (x) obtained by the above equation (3) is equal to or smaller than a predetermined value, or the parameter C (x) obtained by the above equation (3) is changed to the above equation (5). When the value obtained by dividing by SLOP obtained in step 5 is equal to or smaller than a predetermined value, or when the SLOP obtained by equation 5 is equal to or larger than a predetermined value (subject has high contrast), the accuracy of the calculated shift amount is high. Therefore, the focus adjustment by the contrast detection method can be omitted.

  In the above-described embodiment, when the high-frequency component of the image is small and high-precision focus detection by the contrast detection method cannot be expected, focus adjustment by the contrast detection method is omitted. Adjustment can be omitted. For example, when the object scene has a low luminance, the charge accumulation time of the image sensor 22 becomes longer, and the response performance of focus detection also decreases accordingly. Therefore, the focus adjustment by the contrast detection method can be omitted. In addition, when the holding state of the camera body 2 is detected by the shake sensor and the shake becomes equal to or greater than a predetermined value, it can be determined that there is a large blur and strict focus adjustment is unnecessary, so focus adjustment by the contrast detection method is omitted. can do. Furthermore, it is preferable to prioritize focus adjustment with higher response performance over strict focus adjustment when the movement of the subject is detected by analyzing image information over time and the subject movement is greater than or equal to a predetermined value. The focus adjustment by the contrast detection method can be omitted. In addition, when image information is analyzed and a specific subject (for example, a car) is present at the focus detection position, it is preferable to prioritize focus adjustment with high response performance, so that focus adjustment by the contrast detection method is omitted. Can do.

  Conversely, the focus adjustment by the pupil division type phase difference detection method can be omitted depending on the photographing situation. For example, if the focal length of the photographic optical system is short, the difference in image plane between the closest subject and the subject at infinite distance is small, and a large defocus amount does not occur, focus adjustment using the pupil division type phase difference detection method The focus adjustment by the contrast detection method can be performed from the initial stage of the focus adjustment. Also, in the state of step S3 immediately after the power is turned on, if the image contrast is high or the high-frequency component of the image is large, it can be determined that the image is already in focus. The focus adjustment by the detection method can be omitted, and the focus adjustment by the contrast detection method can be performed from the initial stage of the focus adjustment.

  In the above embodiment, when the autofocus mode is the continuous mode, the focus adjustment by the contrast detection method is omitted in order to give priority to the response performance of the focus adjustment operation. However, the contrast is adjusted according to other operation modes of the camera operation. Focus adjustment by the detection method can be omitted. For example, when there are a moving image shooting mode and a still image shooting mode, it is preferable to prioritize the follow-up of focus adjustment in the moving image shooting mode, so focus adjustment by the contrast detection method is omitted. In addition, when there is a mode for shooting a moving subject, such as a sports shooting mode, and a mode for shooting a static subject, such as a landscape shooting mode, the mode for shooting a moving subject has a focus adjustment tracking capability. Since priority is preferred, focus adjustment by the contrast detection method is omitted. Furthermore, if there is a continuous shooting mode that continuously performs shooting operations and a single shooting mode that performs shooting operations only once, it is preferable to prioritize the tracking of focus adjustment in the continuous shooting mode, so contrast detection Focus adjustment by the method is omitted.

  In the above embodiment, the focus detection pixel 222 used for the pupil division type phase difference detection method and the image pickup pixel 221 used for the contrast detection method are arranged on the image pickup surface of the same image pickup device 22. The image sensor used for the phase difference detection method and the image sensor used for the contrast detection method are provided separately, and a light splitting means such as a half mirror is provided in the optical path of the photographing optical system, and the pupil division type position is provided in one of the divided optical paths. An image sensor for performing focus detection by the phase difference detection method may be disposed, and an image sensor for performing focus detection by the contrast detection method may be disposed in the other divided optical path.

  In addition, an image sensor for focus detection by a contrast detection method is arranged on the planned focal plane of the photographing optical system, and a light branching means such as a mirror is inserted in the optical path of the photographing optical system, and the branched optical path An image sensor for focus detection by the pupil division type phase difference detection method may be arranged, and contrast detection may be performed by the image sensor used for the contrast detection method in a state where the branching unit is retracted from the optical path.

  The camera 1 of the present embodiment is not limited to the above-described digital camera with an interchangeable lens, but can be applied to a video camera in addition to a lens-integrated digital still camera, a single-lens reflex camera, and a silver salt film still camera. Further, the present invention can also be applied to a small camera module, a surveillance camera, a robot visual recognition device, and the like built in a mobile phone. Furthermore, the present invention can be applied to a focus detection device, a distance measurement device, a stereo distance measurement device, and the like other than the camera.

It is a principal part block diagram which shows the digital camera which concerns on embodiment of this invention. It is a front view which shows the focus detection position in the imaging surface of the image pick-up element shown in FIG. FIG. 3 is a front view schematically showing an array of focus detection pixels by enlarging the IIIA part of FIG. 2. FIG. 3 is a front view schematically showing an array of focus detection pixels by enlarging a IIIB portion in FIG. 2. It is a front view which expands and shows one of the imaging pixel of FIG. 3A and FIG. 3B. FIG. 4 is an enlarged front view showing one of the focus detection pixels in FIGS. 3A and 3B. It is a spectral characteristic figure which shows the relative sensitivity with respect to each wavelength of three imaging pixel RGB shown to FIG. 3A and 3B. It is a spectral characteristic figure which shows the relative sensitivity with respect to the wavelength of the focus detection pixel 222 shown to FIG. 3A and 3B. 4 is an enlarged cross-sectional view illustrating one of the imaging pixels in FIGS. 3A and 3B. FIG. FIG. 4 is an enlarged cross-sectional view illustrating one of the focus detection pixels in FIGS. 3A and 3B. It is sectional drawing which follows the VIII-VIII line of FIG. 3A and 3B. It is a front view which shows typically the arrangement | sequence of the pixel which concerns on other embodiment of this invention, and is an enlarged front view equivalent to the IIIA part of FIG. It is a front view which shows typically the arrangement | sequence of the pixel which concerns on other embodiment of this invention, and is an enlarged front view equivalent to the IIIB part of FIG. FIG. 10 is an enlarged front view showing a pair of focus detection pixels in FIGS. 9A and 9B. It is a graph for demonstrating the focusing determination of the digital camera which concerns on embodiment of this invention. It is a flowchart which shows the operation example of the camera which concerns on embodiment of this invention. It is a flowchart which shows the operation example of the camera which concerns on embodiment of this invention. It is a graph which shows the relationship between the defocus amount of a camera which concerns on embodiment of this invention, and image shift amount (phase difference amount detected by a pupil division type phase difference detection system). It is a graph for demonstrating the focus detection calculation (defocus amount calculation) procedure of the camera which concerns on embodiment of this invention. It is a graph which shows the relationship between the defocus amount of the camera which concerns on embodiment of this invention, and the contrast evaluation value by a contrast detection system. The upper diagram shows the image waveform of the pixel data with respect to the pixel position of the image sensor of the camera according to the embodiment of the present invention, and the lower diagram shows the waveform obtained by subjecting the image waveform of the upper diagram to the secondary differential filter processing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Digital camera; 2 ... Camera body; 3 ... Lens barrel 21 ... Camera control part; 22 ... Imaging device;
32 ... Focus lens; 36 ... Lens control unit 221 ... Imaging pixel; 222, 222a, 222b ... Focus detection pixel

Claims (21)

An aperture means with an adjustable aperture diameter that restricts a light beam passing through an optical system that forms an image;
Phase difference detection means for detecting an image shift amount by light from different regions of the pupil of the optical system;
Contrast detection means for detecting an evaluation value related to the contrast of the image in association with a focus adjustment position of the optical system;
After adjusting the focus of the optical system based on the amount of deviation of the image in a state where the aperture means is adjusted to the first aperture diameter, the aperture means is moved to a second aperture diameter larger than the first aperture diameter. And a focus adjusting unit that adjusts the focus of the optical system based on the evaluation value in a state adjusted to the above. The focus adjustment device according to claim 1,
The phase difference detection means detects the shift amount of the image at a plurality of focus detection positions on a planned focal plane on which the optical system forms the image,
The focus adjusting unit selects at least one focus detection position from the plurality of focus detection positions based on the image shift amount, and the image shift amount by the phase difference detection unit at the selected focus detection position. The focus adjustment apparatus is configured to adjust the focus of the optical system based on an evaluation value by the contrast detection unit at the selected focus detection position after performing the focus adjustment of the optical system based on. Phase difference detection means for detecting an image shift amount due to light from different regions of the pupil of the optical system at a plurality of focus detection positions on a planned focal plane on which an image is formed by the optical system;
Contrast detection means for detecting an evaluation value relating to the contrast of the image in association with a focus adjustment position of the optical system at the plurality of focus detection positions;
Based on the shift amount of the image at the plurality of focus detection positions, at least one focus detection position is selected from the plurality of focus detection positions, and the image shift by the phase difference detection unit at the selected focus detection position. Focus adjusting means for adjusting the focus of the optical system based on an evaluation value by the contrast detecting means at the selected focus detection position after performing the focus adjustment of the optical system based on the amount. Focus adjustment device characterized by. The focus adjustment device according to claim 3,
A diaphragm means for limiting the luminous flux passing through the optical system and having an adjustable aperture diameter,
The focus adjusting means adjusts the focus by the phase difference detecting means in a state where the aperture means is adjusted to the first aperture diameter, and then sets the aperture means to a second aperture diameter larger than the first aperture diameter. A focus adjusting apparatus, wherein the focus is adjusted by the contrast detection means in a state adjusted to. Phase difference detection means for detecting an image shift amount due to light from different regions of the pupil of the optical system forming the image;
Contrast detection means for detecting an evaluation value related to the contrast of the image in association with a focus adjustment position of the optical system;
After performing the focus adjustment of the optical system based on the shift amount of the image, based on the evaluation value by the contrast detection unit using an image in a range smaller than the detection range of the image used for the focus adjustment, And a focus adjusting means for adjusting the focus of the optical system. The focus adjustment device according to claim 5,
A diaphragm means for limiting the luminous flux passing through the optical system and having an adjustable aperture diameter,
The focus adjusting means adjusts the focus by the phase difference detecting means in a state where the aperture means is adjusted to the first aperture diameter, and then sets the aperture means to a second aperture diameter larger than the first aperture diameter. A focus adjusting apparatus, wherein the focus is adjusted by the contrast detection means in a state adjusted to. The focusing device according to claim 5 or 6,
The phase difference detection means detects the shift amount of the image at a plurality of focus detection positions on a planned focal plane on which the optical system forms the image,
The focus adjusting unit selects at least one focus detection position from the plurality of focus detection positions based on the image shift amount, and the image shift amount by the phase difference detection unit at the selected focus detection position. The focus adjustment of the optical system based on the evaluation value detected by the contrast detection means at the selected focus detection position. apparatus. Phase difference detection means for detecting an image shift amount due to light from different regions of the pupil of the optical system forming the image;
Contrast detection means for detecting an evaluation value related to the contrast of the image in association with a focus adjustment position of the optical system;
A focus for selecting whether or not to perform focus adjustment of the optical system based on an evaluation value by the contrast detection unit according to the characteristics of the image after performing focus adjustment of the optical system based on the image shift amount. And a focus adjustment device. The focus adjustment device according to claim 8, comprising:
A diaphragm means for limiting the luminous flux passing through the optical system and having an adjustable aperture diameter,
The focus adjusting means adjusts the focus by the phase difference detecting means in a state where the aperture means is adjusted to the first aperture diameter, and then sets the aperture means to a second aperture diameter larger than the first aperture diameter. A focus adjusting apparatus, wherein the focus is adjusted by the contrast detection means in a state adjusted to. The focusing device according to claim 8 or 9, wherein
The phase difference detection means detects the shift amount of the image at a plurality of focus detection positions on a planned focal plane on which the optical system forms the image,
The focus adjusting unit selects at least one focus detection position from the plurality of focus detection positions based on the image shift amount, and the image shift amount by the phase difference detection unit at the selected focus detection position. The focus adjustment apparatus is configured to adjust the focus of the optical system based on an evaluation value by the contrast detection unit at the selected focus detection position after performing the focus adjustment of the optical system based on. Phase difference detection means for detecting an image shift amount due to light from different regions of the pupil of the optical system forming the image;
Contrast detection means for detecting an evaluation value related to the contrast of the image in association with a focus adjustment position of the optical system;
After the focus adjustment of the optical system is performed based on the image shift amount by the phase difference detection unit, the focus adjustment of the optical system is performed based on the evaluation value by the contrast detection unit according to the optical characteristics of the optical system. And a focus adjusting means for selecting whether or not. The focus adjustment device according to claim 11, comprising:
A diaphragm means for limiting the luminous flux passing through the optical system and having an adjustable aperture diameter,
The focus adjusting means adjusts the focus by the phase difference detecting means in a state where the aperture means is adjusted to the first aperture diameter, and then sets the aperture means to a second aperture diameter larger than the first aperture diameter. A focus adjusting apparatus, wherein the focus is adjusted by the contrast detection means in a state adjusted to. The focusing device according to claim 11 or 12,
The phase difference detection means detects the shift amount of the image at a plurality of focus detection positions on a planned focal plane on which the optical system forms the image,
The focus adjusting unit selects at least one focus detection position from the plurality of focus detection positions based on an image shift amount by the phase difference detection unit, and the phase difference detection unit at the selected focus detection position. The focus adjustment of the optical system is performed based on the focus evaluation value by the contrast detection means at the selected focus detection position after performing the focus adjustment of the optical system based on the image shift amount by Focusing device. The focus adjustment apparatus according to any one of claims 1 to 10,
The focus adjustment unit selects whether or not to perform focus adjustment by the contrast detection unit according to the optical characteristics of the optical system after performing focus adjustment of the optical system based on the amount of deviation of the image. Focus adjustment device characterized by. It is a focus adjustment apparatus as described in any one of Claims 1-4 or 8-13,
The focus adjustment unit detects an evaluation value by the contrast detection unit using an image in a range smaller than a detection range of the image used for focus adjustment by the phase difference detection unit, and the optical system based on the evaluation value Focus adjustment device characterized in that the focus adjustment is performed. It is a focus adjustment apparatus as described in any one of Claims 1-7 or 11-13,
The focus adjustment unit performs focus adjustment of the optical system based on an amount of deviation of the image, and then selects whether to perform focus adjustment by the contrast detection unit according to the characteristics of the image. Focus adjustment device. The focus adjustment device according to any one of claims 1 to 16,
The phase difference detection means includes a first image sensor in which focus detection pixels having a photoelectric conversion unit that receives a pair of focus detection light beams from different regions of the pupil of the optical system, and output data of the focus detection pixels And a first calculation means for calculating a phase difference between a pair of images formed by the pair of focus detection light beams based on
The contrast detection unit calculates an evaluation value related to a contrast of an image formed by the light flux based on output data of the second imaging element in which imaging pixels that receive the light flux passing through the optical system are arranged and output data of the imaging pixel. And a second calculating means. The focusing device according to claim 17,
The first imaging element and the second imaging element are one imaging element, and the focus detection pixel and the imaging pixel are arranged close to each other on the imaging surface of the same imaging element. Adjusting device. The focusing device according to claim 18, wherein
A plurality of the imaging pixels having different spectral sensitivity characteristics are arranged according to a predetermined arrangement in the one imaging element,
The focus adjustment device, wherein the focus detection pixel is arranged at a position corresponding to an imaging pixel having the highest spectral density characteristic in the array. The focusing device according to claim 8 or 16,
The focus adjustment apparatus characterized in that the characteristic of the image is a spatial frequency characteristic of the image, and when the spatial frequency characteristic of the image is a high frequency equal to or higher than a predetermined value, focus adjustment is performed by the contrast detection unit. The focus adjustment apparatus according to any one of claims 1 to 20,
An image pickup apparatus comprising: an image pickup device that picks up an image through the optical system.

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